Burst receiving circuit and control method thereof

Abstract

A burst receiving circuit and a control method thereof whose unstable state of an output is able to be avoided without bringing about the decrease of the receiving level sensitivity and the deterioration of the output duty are provided. An offset which corresponds to the size of a receiving signal is given to the receiving signal and the offset is made to “0 ” at the time when the burst signal is received and the burst signal is taken out by shaping the receiving signal given offset based on a predetermined threshold value. And the offset is continued to be “0” until predetermined time has passed after finishing the burst signal. The offset is kept in “0” during the time from the start of the burst signal until predetermined time has passed after the finishing of the burst signal or until the finishing of the burst signal informed by the outside.

What is claimed is:  
     
       1. A burst receiving circuit, comprising: 
       a control means for giving an offset which corresponds to the size of a receiving signal to said receiving signal;  
       a signal shaping means for taking out a burst signal by shaping said receiving signal given said offset based on a predetermined threshold value; and  
       an offset switching means which said control means makes said offset “0” at the time when said burst signal is received.  
     
     
       2. A burst receiving circuit in accordance with  claim 1 , comprising: 
       a detecting means for detecting the start of said burst signal at said receiving signal.  
     
     
       3. A burst receiving circuit in accordance with  claim 1 , comprising: 
       a retriggerable multi vibrator which makes the “0” state of said offset continue until predetermined time passes after the finish of said burst signal.  
     
     
       4. A burst receiving circuit in accordance with  claim 2 , comprising: 
       a retriggerable multi vibrator which makes the “0” state of said offset continue until predetermined time passes after the finish of said burst signal.  
     
     
       5. A burst receiving circuit in accordance with  claim 3 , comprising: 
       a flip-flop at which an output is raised by the start of said burst signal and said output is fallen by the finish of said burst signal informed from the outside; and  
       a NAND circuit which makes the “0” state of said offset continue at the case that both outputs of said retriggerable multi vibrator and said flip-flop have been raised.  
     
     
       6. A burst receiving circuit in accordance with  claim 5 , comprising: 
       a light receiving element receiving a light signal; and  
       amplifiers which convert an electric current flowing in said light receiving element to said receiving signal.  
     
     
       7. A burst receiving circuit in accordance with  claim 1 , comprising: 
       a light receiving element receiving a light signal; and  
       amplifiers which convert an electric current flowing in said light receiving element to said receiving signal.  
     
     
       8. A control method of a burst receiving circuit, which comprises giving an offset corresponding to the size of a receiving signal to said receiving signal, making said offset “0” at the time when said burst signal is received, and taking out a burst signal by shaping said receiving signal given said offset based on a predetermined threshold value. 
     
     
       9. A control method of a burst receiving circuit in accordance with  claim 8 , comprising making the “0” state of said offset continue until a predetermined time passes after the finish of said burst signal. 
     
     
       10. A control method of a burst receiving circuit in accordance with  claim 8 , comprising making the state “0” of said offset continue from the start of said burst signal until a predetermined time passes after the finish of said burst signal, or until the finish of said burst signal informed from the outside.